It is well known to construct a scraper-chain conveyor from a series of channels sections or pans joined end-to-end and to circulate a scraper chain assembly along the pans. Each pan can be composed from two shaped, e.g. sigma-shaped, side walls interconnected by a central floor plate. In some cases additional base plates are fitted between lower flanges of the side walls to close off the lower run of the conveyor. To permit access to the lower run it is also known to provide an opening in the floor plate of one or more of the pans and to use detachable plates inset in the openings to close these openings. German patent specification No. 1258333 describes one known construction of this type. The detachable insert plate can be secured in place by means of screws, pins, springs shackles or the like. In the known constructions, the securing means is located on or at the floor plate. During operation of the conveyor, the floor plate is normally subjected to wear which tends to reduce its thickness. The securing means then becomes prone to wear and after a period of time the insert plate cannot be reliably held in place. Moreover, when it is desired to open the access opening by removing the insert plate this can be problematic because the securing means may have suffered wear and/or become blocked by briquetted finings or by corrosion. A general object of the present invention is to provide an improved form of conveyor channel section.